Pervious semi-rigid bobbin of molded plastics material for spools of yarn intended for treatments in dye works

ABSTRACT

On its cylindrical wall the bobbin has adjacent longitudinal rows of holes ( 5 ) of substantially rectangular shape with the short sides ( 5 A) orientated circumferentially and the long sides ( 5 B) curving towards the inside of the hole, the holes in one row being offset with respect to those in adjacent longitudinal rows in such a way as to create undulating longitudinal linear structures ( 9 ) between the longitudinal rows of adjacent holes ( 5 ); the curved longitudinal edges of each hole can lie alongside each other in the intermediate zone following uniform radial compressive stressing of the transverse cross-section of the bobbin, while longitudinal shortening of the bobbin is made easier.

[0001] Bobbins of injection molded plastics material, with perforations so as to render the tubular walls pervious, are also used for treatments in dye works where these bobbins—with the wound spool on them—are subjected to specific stresses, in particular centripedal radial stresses due to the shrinkage which the yarn undergoes during the dyeing treatment. This gives rise to a reduction in the transverse cross-section of the bobbins and also considerable longitudinal elongation which causes complications during the processing stages to which the bobbin is subjected. For this reason it is desirable to have control over the length of the bobbin.

[0002] In a previous patent (Utility Model No. 247,836, filed on Mar. 26, 1999) provision was made for a bobbin which had adjacent longitudinal rows of rectangular or square holes on its cylindrical wall with the holes in one row offset with respect to those in adjacent longitudinal rows in such a way that the longitudinal edges of each hole can be brought near to each other in the intermediate zone as a result of centripedal radial compression stresses, bringing about a substantially uniform reduction in the transverse cross-section of the bobbin; longitudinal shortening of the bobbin is virtually impossible, especially when cold and without simultaneous radial restriction.

[0003] This invention avoids these disadvantages and offers other advantages which will be apparent from a reading of the following text.

[0004] The invention relates to a bobbin of injection molded plastics material for the formation of spools of yarn upon it wound into turns particularly for treatments in dye works and subsequent unwinding of the yarn, the bobbin having adjacent longitudinal rows of holes of substantially rectangular shape along its cylindrical wall with the short sides orientated circumferentially and the long sides curved towards the interior of the hole; in addition to this the holes in one row are offset with respect to those in adjacent longitudinal rows in such a way that the longitudinal linear structures between the longitudinal rows of adjacent holes are undulating. In this way the curved longitudinal edges of each hole can approach each other in the intermediate zone following radial compression stress. This makes possible a substantially uniform reduction in the transverse cross-section of the bobbin as a consequence of the centripedal radial stresses, while longitudinal shortening of the bobbin can easily be controlled, this being encouraged by the undulating shape of the longitudinal linear structures located between adjacent rows of holes.

[0005] The drawing shows one possible embodiment and in particular:

[0006]FIGS. 1 and 2 show the bobbin in question in side view in partial cross-section, in its original configuration and in the configuration deformed after use,

[0007]FIGS. 3 and 4 show two magnified details in FIG. 1, and

[0008]FIG. 5 shows a detail of the manner of axial coupling between superimposed bobbins.

[0009] As illustrated in the appended drawing, a bobbin 1 has in its upper part a contact surface 1B from which there extends a small step 2B followed by the annular terminal zone of cylindrical surface 2 terminating at 2A. One or more relatively slender slots 3, with an orientation slightly inclined with respect to the circumference, are provided in cylindrically shaped zone 2: the slot or slots are defined by outer edges 3A and 3B which incline towards slot 3. Slots 3 and edges 3A and 3B are slightly inclined so as to extend in such a way that they are present over almost the full height of terminal cylindrical zone 2, this zone 2 being designed to receive the turns of the stock yarn. An inner wall 4 defining an intermediate space I within terminal cylindrical zone 2 extends from upper extremity 2A. Reinforcing rings may be provided in intermediate space I between its opposite surfaces.

[0010] Upper terminal cylindrical zone 2 serves to receive a particular number of turns of yarn S indicated in FIG. 5 and indicated diagrammatically and only in part in FIG. 4. At slots 3 and inturned edges 3A and 3B with terminal connections 3C the aforesaid turns are caused to penetrate and concentrate in slot or slots 3 until they come into contact with an inner wall A, and may also be slightly deviated from walls 4 halfway along each of slots 3. Penetration of turns S into slots 3 ensures that the turns of stock yarn S are retained to prevent the possibility of the complex of these turns of stock yarn becoming undone during the handling suffered by the bobbin when the spool of yarn specifically comprising the portion of stock yarn constituted by turns S is formed on it. In addition to this it is easy to remove this yarn from slots 3 when acting on the end of the stock yarn in order to carry out the operations necessary for use of the yarn.

[0011] In order to ensure axial positioning between superimposed spools and space for the turns of stock yarn S on the outer surface of terminal cylindrical zone 2, bobbin 1 is shaped internally at the base 1E (see FIGS. 1, 2 and 4) with a stepped surface 1F. In this way, when two bobbins are superimposed (see also in particular FIG. 5) the terminal edge 1G of base 1E of overlying bobbin 1 is supported on the contact surface 1B of bobbin 1 underneath, but surface 1F of the overlying bobbin is almost in contact with the surface of terminal zone 2 of the bobbin beneath, step 2B ensuring mutual centering of the two superimposed bobbins. This also ensures sufficient space between the surface of zone 2 of the bobbin beneath and stepped inner surface 1F of base 1E of the overlying bobbin to prevent any forcing and deviation of the turns of stock yarn S which are wound onto the surface in upper cylindrical zone 2 of the overlying bobbin when the bobbins are mounted one above the other.

[0012] The central zone intended for winding of the spool of yarn is permeable because of the presence of a plurality of longitudinal rows of holes 5, each of which holes 5 has a shape lying within a rectangular outline. More particularly each hole 5 is defined by two transverse straight short sides 5A and two curved long sides 5B of opposing convexity; short sides 5A of adjacent holes 5 in one longitudinal row of holes define a segment 7 which corresponds substantially to the center of convexity of the curved side 5B of the holes in adjacent rows of holes, the holes in each row being offset by one half step; in other words transverse segments 7 separating holes 5 in each longitudinal row from each other correspond to the intermediate length of curved longitudinal side 5B of holes 5 in the adjacent rows. In order to obtain a half-step shift in holes 5 in one row in comparison with those in adjacent rows, alternate rows have at their ends an upper hole 5X and a lower hole 5Y of very much smaller longitudinal dimensions.

[0013] The shape of the central zone of the bobbin is therefore uniformly permeable with circumferential alignments defined by segments 7 alternating with spaces lying between the central projections of the curvature of sides 5B of adjacent holes 5, while the longitudinal rows of holes 5 are separated by undulating longitudinal linear structures 9 defined by the curved sides 5B of circumferentially adjacent holes 5.

[0014] Both undulating linear structures 9 and transverse segments 7 are relatively slender.

[0015] With this arrangement a structure is obtained which is firstly very permeable in the zone of the central cylindrical wall of the bobbin having holes 5, with the advantage of the uniformity which is effectively achieved when dyeing with liquids which pass through holes 5 from the interior of the bobbin and the mass of yarn wound onto the bobbin in turns. Secondly the structure described is sufficiently rigid and light, with the advantage of requiring a limited quantity of material for formation of the bobbin, for the same strength and rigidity. Thirdly, in the course of the treatment which it undergoes when handling the wound thread and in particular during dyeing treatment, the bobbin in question offers the possibility of easier longitudinal yielding than previously known bobbins having a different hole shape, offering the possibility of reducing the diametral dimensions of the bobbin, before treatment of the yarn wound onto it as well, through stresses caused particularly by the shrinkage which the yarn in the spool wound onto the bobbin undergoes during dyeing treatments. In fact longitudinal linear structures 9, which are slightly undulating, also encourage longitudinal yielding when cold and therefore axial shortening of the bobbin, as well as encouraging restriction of the cross-section of the bobbin in a radial direction during dyeing treatments. 

What I claim is:
 1. An injection molded bobbin of plastics material for the formation of spools of yarn wound into turns on it for processing especially in dye works and subsequent unwinding of the yarn, wherein the cylindrical wall of said bobbin has adjacent longitudinal rows of substantially rectangular holes with the short sides orientated circumferentially and long sides curved inwards towards the hole, and having the holes in one row offset with respect to those in adjacent longitudinal rows in such a way as to create undulating longitudinal linear structures between the longitudinal rows of adjacent holes as a result of which the curved longitudinal edges of each hole can lie alongside each other in the intermediate zone following radial compression stress bringing about a substantially uniform reduction in the transverse cross-section of the bobbin, while longitudinal shortening of the bobbin is made easier as a result of the undulation in the said linear structures.
 2. Bobbin according to claim 1, wherein the holes in the adjacent rows are offset by approximately half a step.
 3. Bobbin according to claim 2, wherein the ends of each bobbin have shapes which are capable of ensuring both mutual centering between axially superimposed bobbins and the formation of a space between the opposite surfaces in order to receive the turns of the stock yarn. 